Unlike last year, when it was easy to bank on a floundering Federer or dominant Nadal, 2014 is a bit offbeat. Wawrinka struck the first errant chord with his win at the Australian Open. A perennial also-ran, Wawrinka worked his way into the top four.

Nadal's win at the French Open and Djokovic's victory at Wimbledon seemed to restore order. That was until Tsonga threw some extra funk in the mix. Then there's old-school Federer, offering a remix with his Edberg-esque serve-and-volley.

If Raonic continues dropping service bombs and Dimitrov keeps shedding his baby Fed, the U.S. Open could see another star born.

Meanwhile, Tsonga leads the field in the U.S. Open Series. His win in Toronto, Raonic's rise up the rankings and Dimitrov's increasing familiarity with later rounds have made the Big Four more mythical than ever.

The Big Four exists, of course. Djokovic, Nadal, Federer and Murray have won 36 of the last 38 Grand Slams.

However, make no mistake, the Big Four's grip on the ATP is slipping. The fourth player, Murray, will be ranked outside the top five. There are also questions about Nadal's U.S. Open readiness after he withdrew from the Rogers Cup and Cincinnati.

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Roger Federer, seen here during the final of the 2014 Rogers Cup, seeks his 18th Grand Slam title.

So why not somebody like Tsonga? His incredible run in Toronto was surprising but far from shocking. He took out three of the Big Four in one week, but he was never a heavy underdog in any of those matches.

Going into the final, Federer held a 11-4 head-to-head edge over Tsonga. To win, Tsonga had to steady his nerves and play his game. He did.

The way in which Tsonga handled the pressure bodes well for his chances at Flushing Meadows. No matter how cruel the draw, it's unlikely he will have to go through four top-10 players in four days.

Djokovic will be playing in his first Slam since getting married. It's unclear if Nadal will even be playing in the U.S. Open.

The retooled Federer and reinvigorated Tsonga are among a fistful of possible winners. Right now, a number of players in the top 15 could snatch a chance and break up the stranglehold the Big Four have at the Slams.

Without a definitive favorite, the U.S. Open becomes even more intriguing, and the fans are the clear winners.